Sorry, teacher's slang (maybe only mine).
I'm giving in on the "a" question --- but now even more convinced the "L" is in no sense my kind of puzzle, ingenious as the structure may have been this week. Back to the realm of sensible challenges!
I found hwk on an Internet Slang website. I'm afraid I still only write the old- fashioned way. My friends laugh as they all text and I don't. It's like a foreign language to me :(